Magnetic shielding apparatus

ABSTRACT

A device in which a magnetic flux field forms a shield of magnetic granules about a shaft member journaled for rotary movement. The shield is arranged to prevent contamination of the shaft member. The foregoing abstract is neither intended to define the invention disclosed in the specification nor is it intended to be limiting as to the scope of the invention in any way.

[ 51 Jan.29, 1974 United States Patent Hanson I 277/80 192/215 6/1966lsakov et e mmfi 1 oe JCL 000 566 9901 111 l// 278 8325 3464 3464 6495,93 2223 MAGNETIC SHIELDING APPARATUS [75] Inventor: William J. Hanson,Pittsford, N.Y.

[73] Assignee: Xerox Corporation, Stamford,

Conn.

Primary Examiner-Morris Kaplan Attorney, Agent, or Firm--James J.Ralabate et al.

[22] Filed: June 28, 1972 [21] Appl. No.: 266,905

[57] ABSTRACT A device in which a magnetic flux field forms a shield ofmagnetic granules about a shaft member journaled for rotary movement.The shield is arranged to prevent contamination of the shaft member.

The foregoing abstract is neither intended to define 08 0 BN N .5 W 0 3Q4 .N G .3/Q 0o "IO-IN 1 m 7 M 5 3 u m m we ""2 n m m .1 m m m0 "8 u mTm hurl N we mm O I f [0 00 r al S M U.mF 1]] 2 00 555 the inventiondisclosed in the specification nor is it intended to be limiting as tothe scope of the invention in any way.

References Cited UNITED STATES PATENTS 14 Claims, 2 Drawing Figures2,809,733 Perry 192/215 MAGNETIC SI'IIELDING APPARATUS BACKGROUND OF THEINVENTION This invention relates generally to a development apparatus ofan electrostatographic printing machine, and more particularly concernsa device for preventing contamination of the development apparatus.

In the process of electrostatographic printing, an electrostatic chargepattern corresponding to an original document to be reproduced isrecorded on an insulating medium. A viewable record is produced bydeveloping the electrostatic charge pattern with particles to form apowder image thereof. Thereafter, the visible powder image is fused tothe insulating medium, or transferred to a suitable support material andfused thereto.

The electrostatic charge pattern or latent image is developed bybringing a developer mix into contact therewith. Various types ofdeveloper mixes may be employed. However, generally, the developer mixcomprises dyed or colored thermoplastic particles, known in the art astoner particles, which are mixed with coarser carrier granules, such asferromagnetic granules. The carrier granules charge the toner particlesto the correct polarity by triboelectrification. As the developer mix isbrought into contact with the electrostatic latent image, the electricfield exerts a force on the charged toner particles. When this force islarge enough to break the carrier-to-toner bond, the toner particlesthen attach themselves to the electrostatic latent image.

Development systems utilize suitable rotary impeller systems or bucketconveyor systems to transport the developer mix from a sump storing asupply thereof to the electrostatic latent image. Impeller systems orconveyor systems generally include shaft members journaled for rotarymovement in suitable rolling contact bearings, i.e., roller or ballbearings, to achieve the requisite movement of developer mix.

The dynamic load characteristics of the bearing generally determine itslife expectancy. Defects in the bearings, mounting, lubrication, orcontamination may accelerate failure and shorten bearing life. Magneticcarrier granules frequentlyenter the bearing and-act as a contaminantthereof. In this manner, the carrier granules contaminate the bearingssupporting the shaft for rotary movement resulting in a reduction in thelife expectancy thereof. This substantially reduces the life expectancyof the conveyor or impeller system and, in turn, that of the developmentapparatus.

Accordingly, it is a primary object of the present invention to improvethe development apparatus by substantially reducing contaminationthereof.

SUMMARY OF THE INVENTION I Briefly stated, and in accordance with thepresent invention, there is provided a device arranged to preventcontamination of a shaft member journaled for rotary movement.

In the particular device illustrated, bearing means rotatably supportthe shaft member with magnetic means being interposed between thebearing means and a flow of magnetic granules. A magnetic flux fieldproduced by the magnetic means entraps and aligns the magnetic granulesinto a shield. Thus, in accordance with the present invention, theshield of granules located between the shaft member and the magneticmeans prevents subsequent granules from contaminating the bearing means.Moreover, the present invention also includes means for impelling thegranules entrapped by the shield in a direction substantially away fromthe bearing means.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of thepresent invention will become apparent upon reading the followingdetailed description and upon reference to the drawings, in which:

FIG. 1 is a sectional elevational view of a development apparatus havingthe present invention therein and adapted for usage in anelectrostatographic printing machine; and

FIG. 2 is a partial, fragmentary sectional view of the shielding deviceused in the development apparatus depicted in FIG. 1.

While the present invention will hereinafter be described in connectionwith a preferred embodiment, it will be understood that it is notintended to limit the invention to that embodiment. On the contrary, itis in- .tended to cover all alternatives, modifications and equivalentsas may be included within the spirit and scope of the invention asdefined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION For a general understanding of theillustrated development apparatus in which the present invention may beincorporated, reference is had to the drawings wherein like referencenumerals have been used throughout to designate like elements. FIG. 1schematically illustrates the development apparatus used in anelectrostatographic printing machine for producing copies from anoriginal document. As in all electrostatographic machines, anelectrostatic latent image is formed on an insulating medium. Developermix is brought into contact with the latent image and toner particlesdeposited thereon to form a powder image thereof. Thereafter, the powderimage is transferred to a sheet of support material to which it may bepermanently adhered by a suitable fusing device. This concept wasoriginally disclosed in US. Pat. No. 2,297,691 issued to Carlson in1942.

The development unit depicted in FIG. 1 is of the type referred to inthe art as a magnetic brush development system." In a magnetic brushdevelopment system, a magnetizable developer mix having carrier granulesand toner particles is continually moved through a directional fluxfield to form a brush of developer material. The brush comprises amagnetic member with a mass of developer mix adhering thereto bymagnetic attraction. This chain-like arrangement of developer mixsimulates the fibers of a brush. Development is achieved by bringing thebrush of developer mix into contact with the electrostatic latent image.

Referring once again to FIG. 1, the principle components of thedevelopment unit depicted therein are developer housing 10, conveyormeans or paddle wheel 12, transport means or roll 14, and developermeans or roll 16. Paddle wheel 12 is a cylindrical member with scoops orbuckets 20 mounted around the periphery thereof. As paddle wheel 12rotates, it elevates developer mix 18 from the lower region or sump ofhousing 10 to the upper region thereof. When developer mix 18 reachesthe upper region of housing 10, it is lifted from buckets 20 totransport roll 14 by the magnetic flux field produced by fixed magnets22 disposed interiorly thereto. Preferably, alternate buckets 20 ofpaddle wheel 12 have apertures in the root diameters thereof enablingdeveloper mix 18 carried in those areas to fall back to the sump ofdeveloper housing 10. As developer mix 18 falls back to the sump, itcascades over shroud 24 which is preferably a tubular member having anaperture or longitudinally extending slot 26 in the lower regionthereof. In this way, developer mix 18 is recirculated such that thecarrier granules thereof are continually agitated to mix with freshtoner particles and generate a strong triboelectric charge therebetween.As developer mix 18, in buckets 20 of paddle wheel 12, approachtransport roll 14 the magnetic flux field produced by magnets 22 mountedfixedly therein attract developer mix 18 thereto. Transport roll 14moves developer mix 18 in an upwardly direction by the frictional forceexerted between the roll surface and developer mix 18. Metering blade 28is provided to control the amount of developer mix 18 carried over thetop of transport roll 14. The surplus developer mix is sheared fromtransport roll 14 and falls in a downwardly direction toward paddlewheel 12. Surplus developer mix falls through the apertures of paddlewheel 12 in a downwardly direction into the sump of developer housing10.

Developer mix 18, which passes metering blade 28, is carried overtransport roll 14 to developer roll 16 and into development zone 30located between photoconductive surface 32 of drum 34 and developer roll16. The electrostatic latent image recorded on photoconductive surface32 is developed by contact with moving developer mix 18. The chargedareas of photoconductive surface 32 electrostatically attract tonerparticles from the carrier granules of developer mix 18. At the exit ofdevelopment zone 30, magnetic fields in a direction generally tangentialto developer roll 16 continue to secure thereto denuded carrier granules(carrier granules which had toner particles stripped therefrom) andunused developer mix. Upon passing from development zone 30, the denudedcarrier granules and unused developer mix enter a region relatively freefrom magnetic forces and fall from developer roll 16 in a downwardlydirection into the lower region of developer housing 10. As the denudedcarrier granules and unused developer mix descend, mixing baffle 36diverts the flow from the ends toward the center of developer housing toprovide mixing in this direction. Paddle wheel 12 includes a shaftmember or hub 38 rotatably mounted on frame member or developer housing18. Buckets are secured fixedly to hub member 38.

Cylindrical shroud 24 serves to control the fall of unused developer mixand denuded carrier granules such that they mix with toner particlesrather than simply falling into the sump of developer housing 10.Furthermore, shroud 24 isolates, from developer mix 18, an interiorcylindrical enclosure which is used to house toner dispenser 40. Tonerdispenser 40 contains a fresh supply of toner particles 42 arranged topass through slot 26 in shroud 24 and into the stream of developer mix18. Having toner particles introduced into the developer mix at thislocation insures that the particles cannot be carried into developmentzone without some degree of mixing with the carrier granules. Additionaltoner particles are added to developer mix 18 in order to replace theparticles used in forming images so as to maintain the concentrationthereof substnatially constant providing substantially uniform imagedevelopability.

Development begins when clutch gear 44 meshes with gear 46 which issecured to paddle wheel 12. Clutch gear 44 rotates in the direction ofarrow 48 to drive gear 46 in the direction of arrow 50, thereby causingpaddle wheel 12 to also revolve in the direction of arrow 58. Inoperation, the development unit positions developer roll 16 adjacent thephotoconductive surface 32 in operative communication therewith todevelop the electrostatic latent image formed thereon with tonerparticles. Thereafter, toner particles are transferred to the supportmaterial forming a toner powder image of the original document thereon.In the preferred embodiment thereof, development roll 16 includesstationary magnets 52 disposed interiorly and arranged to attractdeveloper mix 18 thereto from transport roll 14.

As hereinbefore indicated paddle wheel 12 is journaled for rotarymovement by suitable bearing means such as roller bearings or ballbearings mounted on opposed end portions of hub member 38 providingsupport therefore. Carrier granules may contaminate the bearing memberand reduce the life expectancy of the paddle wheel assembly. In order topreclude the occurrence of the aforementioned carrier granulecontamination, magnetic means are mounted on shroud 24 and developerhousing 10. The aforementioned relation ship between the magnetic meansand bearing means is indicated more clearly in FIG. 2.

As shown in FIG. 2, developer housing 10 includes a generallycylindrical interior surface for housing roller bearing 54. Outer race56 of roller bearing 54 is mounted on the cylindrical interior surfaceof developer housing 10, while inner race 58 of bearing 54 is mounted onhub member 38 of paddle wheel 12. A pair of such bearing members aremounted on hub member 38 in the region of opposed end portions toprovide a simple support therefore. Hence, in this manner, paddle wheel12 is journaled for rotary movement to raise developer mix 18 from thelower region of developer housing 10 to the upper region thereof.Preferably, paddle wheel 10 is interposed between shroud 24 anddeveloper housing 10 and is substantially concentric about thelongitudinal axis of shroud 24. In order to permit the addition of tonerparticles to toner dispenser 40 or the replacement thereof, end cap 60is removably mounted on developer housing 10. As developer mix 18 isadvanced in an upwardly direction, magnetic carrier particles tend tomove toward bearing members 54 resulting in contamination thereof.However, in the present invention, a shield of magnetic carrier particlegranules is formed via the utilization of magnetic means operativelyassociated with impelling means to prevent carrier granules fromcontaminating bearing 54. Magnetic means or ring magnet 62 has theexterior circumferential surface thereof mounted on developer housing 10and is spaced axially from bearing member 54 by arcuate spacer 64. Theinterior circumferential surface of magnetic means 62 is spaced from hubmember 38. Hub member 38 includes a threaded portion 66 aligned so as tobe opposed from magnetic means 62. By way of example, threaded portion66 may be a suit able pipe thread. As carrier granules 68 advance towardbearing member 54 they are attracted to mag netic means or ring magnet62 via the magnetic flux field formed thereby. The magnetic flux fieldis arranged to form a shield of carrier granules between hub member 38and ring magnet 62. As hub member 38 rotates the exterior threadedportion 66 thereof is arranged to impel carrier granules 68 in adirection substantially away from bearing member 54.

In order to further protect bearing member 54 from carrier granulecontamination an interior magnetic member 72 is mounted on shroud 24 inoperative communication with internal threaded portion 74 e.g., asuitable pipe thread, of hub member 38. The magnetic means or ringmagnet 72 has the interior circumferential surface thereof mounted onshroud 24. The exterior circumferential surface of ring magnet 72 isspaced from hub member 38. The interior threaded portion 74 of the hubmember 38 is spaced from and aligned with the exterior circumferentialsurface of ring magnet 72. As carrier granules 68 advance toward bearingmember 54, they are attracted to ring magnet 72. Ring magnet 72 isarranged to form a magnetic flux field which aligns and entraps carriergranules 68 to form shield 71 between the interior circumferentialsurface of hub member 38 and ring magnet 72. Hub member 38 includes aninterior threaded portion 74 substantially aligned with the exteriorcircumferential surface of ring member 72. Threaded portion 74 isadapted to impel carrier granules 68 away from bearing member 54 as hubmember 38 rotates.

From the foregoing, it is apparent that the shielding arrangement of thepresent device substantially improves the development apparatus of anelectrostatographic printing machine by reducing contamination thereof.Furthermore, the carrier granules are prevented from entering thebearing members supporting the paddle wheel in rotary movement, therebyimproving its life expectancy.

It is, therefore, evident that there has been provided in accordancewith this invention, a device for substantially reducing contaminationof the development apparatus of an electrostatographic printing machinethat fully satisfies the objects, aims and advantages set forth above.While this invention has been described in conjunction with specificembodiments thereof, it is evident that many alternatives, modificationsand variations will be apparent to those skilled in the art.Accordingly, it is intended to embrace all alternatives, modificationsand variations that fall within the spirit and broad scope of theappended claims.

What is claimed is:

l. A device for preventing magnetic granules from contaminating atubular shaft member joumaled for rotary movement, including:

bearing means mounted on the shaft member; and

magnetic means disposed externally of and internally of said tubularmember, each said magnetic means being interposed between said bearingmeans and the flow of magnetic granules, said magnetic means producing amagnetic flux field entrapping and aligning the granules into a shieldlocated between the shaft member and said magnetic means to preventgranules from contaminating said bearing means.

2. A device as recited in claim 1, further including means for impellingthe granules entrapped by the shield formed by said magnetic means in adirection substantially away from said bearing means.

3. A device as recited in claim 2, further including a frame memberadapted to support said bearing means so as to enable the shaft memberto rotate relative thereto. I

4. A device as recited in claim 3, wherein said magnetic means includesa magnet member mounted on the shaft member spaced from said framemember.

5. A device as recited in claim 4, wherein said impelling means includesa threaded portion on said frame member aligned generally opposed fromsaid magnetic member and spaced therefrom, said threaded portion beingadapted to move the entrapped granules in a direction substantially awayfrom said bearing means as the shaft member rotates.

6. A device as recited in claim 3, wherein said magnetic means includesa magnet member mounted on said frame member spaced from the shaftmember.

7. A device as recited in claim 6, wherein said impelling means includesa threaded portion on the shaft member aligned generally opposed fromsaid magnet member and spaced therefrom, said threaded portion beingadapted to move the entrapped granules in a direction substantially awayfrom said bearing means as the shaft member rotates.

8. A development apparatus for an electrostatographic printing machineof the type having conveyor means for transporting a developer mixcomprising magnetic carrier granules and toner particles into contactwith an electrostatic latent image to create a toner powder imagethereof, wherein the improvement includes:

a tubular rotary driven shaft member;

bearing means for rotatably supporting said shaft member; and

magnetic means disposed externally of and internally of said tubularmember, each said magnetic means being interposed between said bearingmeans and the flow of carrier granules, said magnetic means producing amagnetic flux field entrapping and aligning the carrier granules into ashield located between said shaft member and said magnetic means toprevent granules from contaminating said bearing means.

9. An apparatus as recited in claim 8, further including means forimpelling the granules entrapped by the shield formed by said magneticmeans in a direction substantially away from said bearing means.

10. An apparatus as recited in claim 9, further including a frame memberadapted to support said bearing means so as to enable said shaft memberto rotate relative thereto.

11. An apparatus as recited in claim 10, wherein said magnetic meansincludes a magnet member mounted on said shaft member spaced from saidframe member.

12. An apparatus as recited in claim 11, wherein said impelling meansincludes a threaded portion on said frame member aligned generallyopposed from said magnetic member and spaced therefrom, said threadedportion being adopted to move the entrapped granules in a directionsubstantially away from said bearing means as said shaft member rotates.

13. An apparatus as recited in claim 10, wherein said magnetic meansincludes a magnetic member mounted on said frame member spaced from saidshaft member.

14. An apparatus as recited in claim 13, wherein said impelling meansincludes a threaded portion on said shaft member aligned generallyopposed from said magnetic member and spaced therefrom said threadedportion being adapted to move the entrapped granules in a directionsubstantially away from said bearing means as said shaft member rotates.

1. A device for preventing magnetic granules from contaminating a tubular shaft member journaled for rotary movement, including: bearing means mounted on the shaft member; and magnetic means disposed externally of and internally of said tubular member, each said magnetic means being interposed between said bearing means and the flow of magnetic granules, said magnetic means producing a magnetic flux field entrapping and aligning the granules into a shield located between the shaft member and said magnetic means to prevent granules from contaminating said bearing means.
 2. A device as recited in claim 1, further including means for impelling the granules entrapped by the shield formed by said magnetic means in a direction substantially away from said bearing means.
 3. A device as recited in claim 2, further including a frame member adapted to support said bearing means so as to enable the shaft member to rotate relative thereto.
 4. A device as recited in claim 3, wherein said magnetic means includes a magnet member mounted on the shaft member spaced from said frame member.
 5. A device as recited in claim 4, wherein said impelling means includes a threaded portion on said frame member aligned generally opposed from said magnetic member and spaced therefrom, said threaded portion being adapted to move the entrapped granules in a direction substantially away from said bearing means as the shaft member rotates.
 6. A device as recited in claim 3, wherein said magnetic means includes a magnet member mounted on said frame member spaced from the shaft member.
 7. A device as recited in claim 6, wherein said impelling means includes a threaded portion on the shaft member aligned generally opposed from said magnet member and spaced therefrom, said threaded portion being adapted to move the entrapped granules in a direction substantially away from said bearing means as the shaft member rotates.
 8. A development apparatus for an electrostatographic printing machine of the type having conveyor means for transporting a developer mix comprising magnetic carrier granules and toner particles into contact with an electrostatic latent image to create a toner powder image thereof, wherein the improvement includes: a tubular rotary driven shaft member; bearing means for rotatably supporting said shaft member; and magnetic means disposed externally of and internally of said tubular member, each said magnetic means being interposed between said bearing means and the flow of carrier granules, said magnetic means producing a magnetic flux field entrapping and aligning the carrier granules into a shield located between said shaft member and said magnetic means to prevent granules from contaminating said bearing means.
 9. An apparatus as recited in claim 8, further including means for impelling the granules entrapped by the shield formed by said magnetic means in a direction substantially away from said bearing means.
 10. An apparatus as recited in claim 9, further including a frame member adapted to support said bearing means so as to enable said shaft memBer to rotate relative thereto.
 11. An apparatus as recited in claim 10, wherein said magnetic means includes a magnet member mounted on said shaft member spaced from said frame member.
 12. An apparatus as recited in claim 11, wherein said impelling means includes a threaded portion on said frame member aligned generally opposed from said magnetic member and spaced therefrom, said threaded portion being adopted to move the entrapped granules in a direction substantially away from said bearing means as said shaft member rotates.
 13. An apparatus as recited in claim 10, wherein said magnetic means includes a magnetic member mounted on said frame member spaced from said shaft member.
 14. An apparatus as recited in claim 13, wherein said impelling means includes a threaded portion on said shaft member aligned generally opposed from said magnetic member and spaced therefrom said threaded portion being adapted to move the entrapped granules in a direction substantially away from said bearing means as said shaft member rotates. 